The invention relates to a method for exchanging signals in a communication network. The invention further relates to a communication system which is connectable to a public telecommunication network.
A conventional public telecommunications network is based on that telephones and other communication arrangements are connected to the telecommunication network exchange by means of fixed wire connections. The signals, for example inputted telephone numbers, which are generated by the telephones, are delivered in a standardised way via the wire connections to an exchange in the telecommunication network. It is further known to connect specially adapted telephones with the public telecommunications network via a radio connection.
U.S. Pat. No. 5,117,450 describes a specially adapted telephone comprising a radio transceiver and a microcomputer with a memory. When a telephone conversation is to be initiated by the telephone, each inputted digit is stored in the memory, and a check of validity of the inputted telephone number is locally performed in the telephone before the connection is established with the telephone number that was input. This telephone must consequently be equipped with a lot of information on the different number combinations which are valid and the amount of the information becomes considerable in order to permit international telephone conversations as well.
British Patent No. 1 115 315 describes a first arrangement which comprises a telephone handset which is coupled to a relay-controlled radio transmitter and to a first radio receiver. When a telephone conversation is to be initiated from the telephone handset, the radio transmitter is activated by sending a precise tone signal via radio to a second receiver which is included in a second arrangement. The second arrangement is connected to a telephone line. The second receiver delivers the received tone signal to a filter which is selectively sensitive to a certain tone, and when the filter indicates the reception of the precise tone signal, it activates a relay which switches on a second radio transmitter in order to send a dial tone to the radio receiver of the telephone handset.
WO 95/15664 describes a radiotelephone system comprising a subscriber unit which in a wireless manner communicates with a Local Access Mobility Manager (LAMM). The LAMM is connected to a Local Exchange. According to WO95/15664 the subscriber unit sends a disconnect message to the LAMM when a customer ends a call. The LAMM sends a release message to the subscriber unit. The subscriber unit sends a release complete message to the LAMM, and the LAMM returns the radio channel to idle.